Light-emitting diode (LED) lighting technology is known for delivery of increased power efficiency with associated reductions in cost particularly in commercial applications, such as for example in street lighting where previously inefficient/high cost HID sodium lamps were utilised.
From a commercial perspective, and particularly from the viewpoint of potential implementation of LED arrays in large-scale commercial applications, such as for example in industrial applications or in large retail applications, it would clearly be of considerable benefit if such LED array(s) could be operated on a more energy efficient basis, and in a cost-efficient manner whilst providing the capacity for remote control of their wavelength, radiant intensities and photoperiods.
Commercially available LED lights are powered with DC current that means that they are typically placed in close proximity to an AC/DC inverter, typically 230 v AC-24 v DC. At low voltage DC there is a significant voltage drop over short distances which mean that for system efficiency the AC/DC invertor must be placed at a distances from the LED lights of less than 5 m, and typically about 2 m.
A particular disadvantage of using LED-based lighting for the provision of lighting for large-scale commercial or industrial applications, or high intensity lighting systems which require high numbers of LED lights, is that the necessary spacing between either the individual LED lights or between groups of the LED lights means that the distance between the AC/DC inverters needs to increase because such arrangements typically mean that the risk of DC voltage drop is increased. The Applicant has recognised that such risk of DC voltage drop is applicable to any DC-powered lighting device.
To date efforts to resolve this voltage drop issue for commercial applications have provided modified lighting systems which utilise LED lights, and particularly strips of LED lights, also known as strip lighting in association with an increased number of AC/DC inverters which are smaller in size. In addition to the LED costs indicated hereinbefore, and the additional inverter costs, such modified systems require far higher quantities of high voltage AC wiring, to connect to multiple inverters, than would be required if using a single large AC/DC inverter. This is particularly expensive in large-scale commercial systems, such as systems for use in large-scale industrial applications or complex commercial applications where all wiring and inverters must be IP rated. In addition, the complexity of such systems means that the measures required for controlling the LED lighting within such modified systems, as well as the measurement of wavelength, intensity and photoperiod generated becomes impractical as well as potentially hazardous should any fault occur.
At present, the industry standard AC/DC inverters for use with LED lights have power factors (PF) typically in the range 0.7 to 0.9. There would be however a considerable financial benefit to increasing the power factor to close to 1.0.
Total harmonic distortions (THDs) of 20% or less, are considered acceptable in the provision of LED lighting. It would be of considerable benefit to provide a system that could reduce or eliminate THD because any THD is both potentially damaging to animal and human health and interferes with other electronic systems.
Thus, there is a need to provide a system for the provision of power and lighting to lighting devices which are adapted to be powered by DC, and especially to LED-based lighting systems containing one or more LED-lighting devices, such as LED arrays which overcomes the voltage-drop restrictions of current systems and is capable of delivering radiant power distribution in a uniform manner, with improved power conversion versus the presently available conventional compact or strip-style LED lighting arrays and which is provided improved (increased) PF and/or reduced or no THD.
One of the desirable features of LED fixtures is the ability to control each wavelength independently and to vary the intensities and the photoperiods according to the specific needs of the customised commercial or domestic system.
It is technically possible using LEDs to adjust the photoperiods from milliseconds to hours. LED lighting manufacturers have designed compact LED lighting arrays using conventional printed circuit boards (PCBs) often incorporating 100's of high powered LEDs. These are IP rated and supplied by high voltage, typically 240 v AC.
As over 50% of the power supplied to such LED arrays is typically converted to heat rather than radiant power, these compact LED lighting arrays are often air cooled with fans. Given the ever-increasing awareness of both domestic and commercial consumers of the environmental cost associated with wasted energy consumption, the relative inefficiency of the power conversion provided by commercially available LED arrays can be a deterrent to their use in some circumstances.
Thus, there is a need to provide a power system for such LED lighting arrays which converting more than 50% of the power supplied to radiant power rather than heat energy.